diff --git a/docs/userguide.rst b/docs/userguide.rst
index f4c6c7e..403d866 100644
--- a/docs/userguide.rst
+++ b/docs/userguide.rst
@@ -77,6 +77,13 @@ Environment variables
 | ``KAS_TARGET``        |                                                     |
 | ``KAS_TASK``          |                                                     |
 +-----------------------+-----------------------------------------------------+
+| ``KAS_PREMIRRORS``    | Specifies alternatives for repo URLs. Just like     |
+|                       | bitbake ``PREMIRRORS``, this variable consists of   |
+|                       | new-line separated entries. Each entry defines a    |
+|                       | regular expression to match a URL and, space-       |
+|                       | separated, its replacement. E.g.:                   |
+|                       | "https://.*\.somehost\.io/ https://localmirror.net/"|
++-----------------------+-----------------------------------------------------+
 | ``SSH_PRIVATE_KEY``   | Path to the private key file that should be added   |
 |                       | to an internal ssh-agent. This key cannot be        |
 |                       | password protected. This setting is useful for CI   |
diff --git a/kas-docker b/kas-docker
index 993b2eb..56ad506 100755
--- a/kas-docker
+++ b/kas-docker
@@ -213,7 +213,8 @@ fi
 set -- ${DOCKER_ARGS}
 
 for var in SHELL TERM KAS_DISTRO KAS_MACHINE KAS_TARGET KAS_TASK \
-           http_proxy https_proxy ftp_proxy no_proxy NO_PROXY; do
+           http_proxy https_proxy ftp_proxy no_proxy NO_PROXY \
+           KAS_PREMIRRORS; do
 	if [ -n "$(eval echo \$${var})" ]; then
 		set -- "$@" -e "${var}='$(eval echo \"\$${var}\")'"
 	fi
diff --git a/kas/repos.py b/kas/repos.py
index add94dc..0596520 100644
--- a/kas/repos.py
+++ b/kas/repos.py
@@ -23,6 +23,7 @@
     This module contains the Repo class.
 """
 
+import re
 import os
 import asyncio
 import logging
@@ -62,6 +63,16 @@ class Repo:
                     .replace(':', '.')
                     .replace('/', '.')
                     .replace('*', '.'))
+        elif item == 'effective_url':
+            mirrors = os.environ.get('KAS_PREMIRRORS', '')
+            for mirror in mirrors.split('\n'):
+                try:
+                    expr, subst = mirror.split()
+                    if re.match(expr, self.url):
+                        return re.sub(expr, subst, self.url)
+                except ValueError:
+                    continue
+            return self.url
         # Default behaviour
         raise AttributeError
 
@@ -273,7 +284,7 @@ class GitRepo(RepoImpl):
     """
 
     def clone_cmd(self, gitsrcdir):
-        cmd = ['git', 'clone', '-q', self.url, self.path]
+        cmd = ['git', 'clone', '-q', self.effective_url, self.path]
         if get_context().kas_repo_ref_dir and os.path.exists(gitsrcdir):
             cmd.extend(['--reference', gitsrcdir])
         return cmd
@@ -308,7 +319,7 @@ class MercurialRepo(RepoImpl):
     """
 
     def clone_cmd(self, gitsrcdir, config):
-        return ['hg', 'clone', self.url, self.path]
+        return ['hg', 'clone', self.effective_url, self.path]
 
     def contains_refspec_cmd(self):
         return ['hg', 'log', '-r', self.refspec]